Technical Field
[0001] The present invention relates to a sealing device for a differential mechanism, and
particularly relates to a sealing device for a differential mechanism that is used
for an output shaft of the differential mechanism in vehicles, general purpose machines,
and the like.
Background Art
[0002] In a vehicle, for example an automobile, a differential mechanism for absorbing a
difference in rotational speed between right and left driving wheels during turning
of the vehicle is provided. The differential mechanism is housed in a housing of a
transaxle or a differential device. In the differential mechanism, a drive force input
through a drive shaft is respectively distributed through axles serving as right and
left output shafts. In the housing, the axles are supported by bearings, and lubricant
for lubricating the difference mechanism and the bearings is stored in the housing.
Each of the axles is inserted through a through-hole formed in the housing, and sealing
of the through-hole is attempted to be sealed by a sealing device.
[0003] Fig. 10 is a cross-sectional view for illustrating a schematic configuration of a
conventional sealing device for a differential mechanism (hereinafter simply referred
to as a "sealing device") that is used for a differential mechanism. Fig. 11 is a
cross-sectional view of the conventional sealing device illustrated in Fig. 10 in
a state of being attached to a differential mechanism provided in a transaxle, for
example. As illustrated in Fig. 10, a conventional sealing device 100 includes an
annular reinforcing ring 101, and an annular elastic body part 102 formed from an
elastic body that is integrally formed with the reinforcing ring 101, and the elastic
body part 102 includes a seal lip 103, a dust lip 104, and a side lip 105. As illustrated
in Figs. 10, 11, the seal lip 103 is in slidable contact with an axle 111 of a differential
mechanism 110 to thereby prevent the lubricant in a housing 112 in which the differential
mechanism 110 is housed from leaking out. The dust lip 104 is formed outside the seal
lip 103, and is in slidable contact with the axle 111 to thereby prevent foreign matter
such as muddy water, rainwater, and dust from entering into the housing 112 from the
outer side. As illustrated in Fig. 10, the side lip 105 extends toward the outer side
on an outer periphery side of the dust lip 104, and has a conical cylindrical shape
that increases in diameter toward an outward side at a constant angle. As illustrated
in Fig. 11, the side lip 105, at a distal end edge, slidably contacts a disc-shaped
sliding surface 113a, facing the inner side, of an annular deflector 113 fixed to
the axle 111 in such a manner that the deflector 113 is slidable, to thereby prevent
foreign matter from entering from the outer side. The side lip 105 is elastically
deformed and curved in a state of being in contact with the deflector 113, and an
inner peripheral surface of the distal end edge is formed so as to be in contact with
the sliding surface 113a of the deflector 113.
[0004] The sealing device 100 is attached between a through-hole 114 in the housing 112
in which the differential mechanism 110 is housed and the axle 111 inserted through
the through-hole 114 in order to seal the through-hole 114, thereby preventing the
lubricant stored in the housing 112 from leaking out to the outer side, and preventing
the foreign matter from entering into the housing 112 (for example, see Patent Literature
1).
Citation List
Patent Literature
[0005] Patent Literature 1: Japanese Patent Application Publication No.
2014-126173
Summary of Invention
Technical Problem
[0006] In the conventional sealing device 100 for a differential mechanism as described
above, the axle 111 is displaced about an axis of the axle 111 within a minute range
during operation based on a gap between members in the differential mechanism 110
and a device such as the transaxle that is provided with the differential mechanism
110, and the axle 111 is displaced from a desired position based on dimensional tolerance
and assembly errors of members in the differential mechanism 110 and the device provided
with the differential mechanism 110. Therefore, the side lip 105 is further elastically
deformed and curved corresponding to the displacement (looseness) of the axle 111
such that a middle portion that is a portion on a root side relative to the distal
end of the side lip 105 is in contact with the deflector 113, or the deformation of
the side lip 105 is relieved so that the side lip 105 is gently curved to maintain
a contact state with the deflector 113 following the movement of the deflector 113,
with the result that the prevention of the entering of dust is maintained.
[0007] However, when the looseness of the axle 111 of the differential mechanism 110 is
large, the side lip 105 is more largely curved, and a contact width between the side
lip 105 and the deflector 113 is increased. The side lip 105 is also in contact with
the deflector 113 at a middle portion that is a portion closer to the root side, a
contact pressure to the deflector 113 is increased at the middle portion, and the
contact pressure to the deflector 113 is reduced at the distal end of the side lip
105. As shown in Fig. 12, a difference (pressure difference Δpc) between the contact
pressure at the distal end and the contact pressure at the middle portion on the root
side is reduced, and the distal end of the side lip 105 may float away from the deflector
113. If the distal end of the side lip 105 repeatedly floats away from the deflector
113 due to the looseness of the axle 111 during operation of the differential mechanism
110, the distal end of the side lip 105 may cause the foreign matter to enter the
inner side, and enter the housing 112, In recent years, there has been required a
sealing device having a configuration capable of coping with a greater looseness of
the axle 111 of the differential mechanism 110, but in the conventional sealing device
100 for a differential mechanism as described above, if a great looseness of the axle
111 occurs in the differential mechanism 110, the contact width is increased, the
distal end of the side lip 105 floats away from the deflector 113, and therefore the
foreign matter may enter into the inner side of the differential mechanism 110.
[0008] As described above, in the conventional sealing device 100 for a differential mechanism,
there has been required a configuration capable of preventing the distal end of the
side lip 105 from floating away from the deflector 113 even when the contact width
is increased.
[0009] The present invention has been made in view of the above problems, and it is an object
of the present invention to provide a sealing device for a differential mechanism
capable of preventing a distal end of a side lip from floating away from a deflector
even when a contact width of the side lip is increased.
Solution to Problem
[0010] To achieve the above object, a sealing device for a differential mechanism according
to the present invention is a sealing device for a differential mechanism for sealing
between a through-hole formed in a housing in which the differential mechanism is
housed and an output shaft of the differential mechanism that is rotatably inserted
through the through-hole, the sealing device for a differential mechanism characterized
in including an annular reinforcing ring centered about an axis, and an annular elastic
body part formed from an elastic body centered about the axis that is attached to
the reinforcing ring. The elastic body part has an annular seal lip that is in contact
with the output shaft such that the output shaft is slidable, an annular dust lip
that is provided at the outer side of the seal lip, the dust lip is in contact with
the output shaft such that the output shaft is slidable, and an annular side lip that
extends toward the outer side on an outer periphery side of the dust lip that is in
contact with an annular deflector attached to the output shaft such that the deflector
is slidable. The side lip has an annular middle portion that increases in diameter
toward an outer side in a direction of the axis, and an annular distal end portion
that is a portion connected to the middle portion and is the outer side of the middle
portion, and increases in diameter toward an outer side in the direction of the axis,
in which at least the distal end portion of the distal end portion and the middle
portion is in contact with the deflector. And The distal end portion of the side lip
is bent to an inner periphery side from the middle portion.
[0011] In the sealing device for a differential mechanism according to one aspect of the
present invention, the distal end portion of the side lip is bent from the middle
portion, dimensions of the distal end portion are set, and a physical property of
the elastic body forming the elastic body part is set so that a contact pressure to
the deflector at the distal end portion with respect to a contact pressure to the
deflector at the middle portion is set in a manner such that a contact between the
distal end of the side lip and the deflector is not released.
[0012] In the sealing device for a differential mechanism according to one aspect of the
present invention, a thickness of the distal end portion of the side lip is set based
on a hardness of the elastic body.
[0013] In the sealing device for a differential mechanism according to one aspect of the
present invention, the distal end portion has a conical cylindrical shape centered
about the axis, and the middle portion has a conical cylindrical shape centered about
the axis.
[0014] In the sealing device for a differential mechanism according to one aspect of the
present invention, the side lip has an annular root portion that extends in the direction
of the axis, and the middle portion is a portion that is connected to the root portion
and is outside the root portion.
Effects of Invention
[0015] According to a sealing device for a differential device of the present invention,
a distal end of a side lip can be prevented from floating away from a deflector even
when a contact width of the side lip is increased.
Brief Description of Drawings
[0016]
[Fig. 1] Fig. 1 is a cross-sectional view taken along an axis for illustrating a schematic
configuration of a sealing device for a differential mechanism according to an embodiment
of the present invention.
[Fig. 2] Fig. 2 is a partial enlarged cross-sectional view of the sealing device illustrated
in Fig. 1.
[Fig. 3] Fig. 3 is a diagram for illustrating the sealing device illustrated in Fig.
1 in a state of being attached to a transaxle housing the differential mechanism,
and a partial enlarged cross-sectional view along an axis x enlargedly illustrating
a vicinity of the sealing device in the transaxle.
[Fig. 4] Fig. 4 is an enlarged cross-sectional view of a side lip for illustrating
a state of the side lip in a state where the sealing device is attached to a desired
position of the transaxle.
[Fig. 5] Fig. 5 is an enlarged cross-sectional view of the side lip for illustrating
a state of the side lip in a state where an axle of the differential mechanism is
displaced.
[Fig. 6] Fig. 6 is a diagram of a graph showing a relationship between a contact width
and a contact pressure of the side lip with a deflector in a state illustrated in
Fig. 5.
[Fig. 7] Fig 7 is a diagram for illustrating a schematic configuration of a sealing
performance tester used for an evaluation test of sealing performance in the sealing
device for a differential mechanism.
[Fig. 8] Fig. 8 is a diagram for showing results of the evaluation test of the sealing
performance of a conventional sealing device, Fig. 8(a) is a diagram illustrating
a projection image of the side lip in the evaluation test of the sealing performance,
and Fig. 8(b) is a diagram showing the relationship between the contact position and
the contact pressure of the side lip.
[Fig. 9] Fig. 9 is a diagram for showing results of the evaluation test of the sealing
performance of the sealing device according to the embodiment of the present invention,
Fig. 9(a) is a diagram illustrating a projection image of the side lip in the evaluation
test of the sealing performance, and Fig. 9(b) is a diagram showing the relationship
between the contact position and the contact pressure of the side lip.
[Fig. 10] Fig. 10 is a cross-sectional view for illustrating a schematic configuration
of a conventional sealing device for a differential mechanism that is used for a differential
mechanism.
[Fig. 11] Fig. 11 is a cross-sectional view for illustrating the conventional sealing
device for a differential mechanism illustrated in Fig. 10 in a state of being attached
to a differential mechanism provided in a transaxle.
[Fig. 12] Fig. 12 is a diagram showing a relationship between a contact width and
a contact pressure of the side lip with the deflector in the conventional sealing
device for a differential mechanism.
Description of Embodiments
[0017] Hereinafter, embodiments of the present invention will be described with reference
to the drawings.
[0018] Fig. 1 is a cross-sectional view taken along an axis x for illustrating a schematic
configuration of a sealing device for a differential mechanism (hereinafter simply
referred to as a "sealing device") according to an embodiment of the present invention.
Fig. 2 is a partial enlarged cross-sectional view of the sealing device illustrated
in Fig. 1. A sealing device 1 according to the embodiment of the present invention
is used for a device provided with a differential mechanism for absorbing a difference
in rotational speed between right and left driving wheels during turning of a vehicle,
a general purpose machine, or the like. Examples of a device provided with a differential
mechanism include a transaxle, a differential device, and in the present embodiment,
the sealing device 1 is used for the transaxle. More particularly, in the transaxle,
the sealing device 1 is used for sealing between a through-hole formed in a housing
and an axle as an output shaft of the differential mechanism that is rotatably inserted
through the through-hole, as described later.
[0019] Hereinafter, a direction directed by an arrow a in a direction of the axis x (see
Fig. 1) represents an outer side, and a direction directed by an arrow b in the direction
of the axis x (see Fig. 1) represents an inner side, for convenience of explanation.
More particularly, the outer side means a side facing the outside of the housing in
the transaxle provided with a differential mechanism, and an atmosphere side, and
the inner side means a side facing the inside of the housing in the transaxle. In
a direction perpendicular to the axis x (hereinafter also referred to as a "radial
direction"), a direction away from the axis x (a direction directed by an arrow c
in Fig. 1) represents an outer periphery side, and a direction approaching the axis
x (a direction directed by an arrow d in Fig. 1) represents an inner periphery side.
[0020] The sealing device 1 includes an annular reinforcing ring 10 centered about the axis
x, and an annular elastic body part 20 formed of an elastic body centered about the
axis x, as illustrated in Fig. 1. The elastic body part 20 is integrally attached
to the reinforcing ring 10. The reinforcing ring 10 is formed of a metal material.
Examples of the metal material include stainless steel, and SPCC (cold rolled steel
sheet). Examples of the elastic body of the elastic body part 20 include various rubber
materials. The various rubber materials are, for example, synthetic rubber such as
nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), acrylic rubber (ACM), and
fluororubber (FKM).
[0021] The reinforcing ring 10 is manufactured by press working or forging, for example,
and the elastic body part 20 is molded with a mold by cross-linking (vulcanization).
During the cross-linking, the reinforcing ring 10 is placed in the mold, the elastic
body part 20 is bonded to the reinforcing ring 10 by cross-linking bonding, and the
elastic body part 20 is integrally molded with the reinforcing ring 10.
[0022] As illustrated in Figs. 1 and 2, a shape of a cross section along the axis x (hereinafter
simply referred to as a "cross section") of the reinforcing ring 10 is a substantially
L shape, for example, and the reinforcing ring 10 includes a cylindrical part 11 that
is a cylindrical portion extending in the direction of the axis x, and a flange part
12 that is a hollow disc-shaped portion expanding toward the inner periphery side
from the outer end portion of the cylindrical part 11. The cylindrical part 11 is
formed so as to be able to be fitted to an inner peripheral surface of the through-hole
formed in the housing of the transaxle, as described later. The cylindrical part 11
may be directly in contact with the inner peripheral surface of the through-hole to
be able to be fitted to the inner peripheral surface of the through-hole, or may be
in contact with the inner peripheral surface of the through-hole through a portion
of the elastic body part 20 to be able to be fitted to the inner peripheral surface
of the through-hole.
[0023] As illustrated in Figs. 1 and 2, the elastic body part 20 is attached to the reinforcing
ring 10, and is integrally formed with the reinforcing ring 10 to cover the entire
reinforcing ring 10 in the present embodiment. The elastic body part 20 includes an
annular seal lip 21, an annular dust lip 22, and an annular side lip 23. The elastic
body part 20 also includes an annular lip waist portion 24. The seal lip 21 is formed
so as to be in contact with an axle of the differential mechanism so that the axle
is slidable, as described later, and the dust lip 22 is provided on the outer side
of the seal lip 21 and formed so as to be in contact with the axle so that the axle
is slidable. The side lip 23 is formed so as to be in contact with an annular deflector
fixed to the axle so that the deflector is slidable, and extends toward the outer
side on the outer periphery side of the dust lip 22 as described later. In the elastic
body part 20, the lip waist portion 24 is a portion positioned in the vicinity of
an end portion on the inner periphery side of the flange part 12 of the reinforcing
ring 10.
[0024] The seal lip 21 is a portion that extends toward the inner side from the lip waist
portion 24, and an annular portion centered about the axis x, and is formed by facing
the cylindrical part 11 of the reinforcing ring 10, as illustrated in Figs. 1 and
2. The seal lip 21 has an annular lip distal end portion 25 at an inner end portion,
the lip distal end portion 25 having a cross section formed in a wedge shape projecting
toward the inner periphery side. A garter spring 26 is fitted at a position facing
away from the lip distal end portion 25 on the outer periphery side of the seal lip
21, and the garter spring 26 presses the lip distal end portion 25 of the seal lip
21 toward the inner periphery side in the radial direction to apply a tensional force
of a predetermined magnitude against the axle to the lip distal end portion 25. The
lip distal end portion 25 is in contact with an outer peripheral surface of the axle
to seal between the sealing device 1 and the axle, as described later. As illustrated
in Fig. 1, a plurality of screw projections 25b are spirally formed at an equal angle
interval in a circumferential direction on a taper surface 25a of a conical surface
shape of the lip distal end portion 25 on the outer side, the screw projections 25b
extending diagonally with respect to the distal end of the lip distal end portion
25 and projecting in an inner peripheral direction. The screw projections 25b generate
air flow from the outside to the inner side when the axle is slided, to thereby prevent
lubricant from leaking from the inside.
[0025] The dust lip 22 extends outwardly from the lip waist portion 24 and toward the axis
x, more particularly, as illustrated in Figs. 1, 2, the dust lip 22 extends in a direction
toward the outer side and the inner periphery side from the lip waist portion 24.
The dust lip 22 prevents foreign matter such as muddy water, sand, and dust from entering
in a direction toward the lip distal end portion 25 in the usage state. In the dust
lip 22, in order that a negative pressure is not generated in a space between the
dust lip 22 and the seal lip 21 in the usage state, a plurality of projections 22a
projecting in the inner peripheral direction are formed at an equal angle interval
in a circumferential direction so that a gap is formed by partially releasing the
contact between the dust lip 22 and the axle to thereby suppress the generation of
the negative pressure or eliminate the negative pressure.
[0026] The elastic body part 20 includes a gasket part 27, a rear cover part 28, and a lining
part 29. In the elastic body part 20, the gasket part 27 is a portion that covers
the cylindrical part 11 of the reinforcing ring 10 from the outer periphery side.
As described later, the thickness in the radial direction of the gasket part 27 is
set so that, when, in the transaxle, the sealing device 1 is pressed into a through-hole
through which the axle is inserted, the gasket part 27 is pressed between the through-hole
and the cylindrical part 11 of the reinforcing ring 10 in the radial direction so
that the gasket part 27 generates a fitting force of a force outward in a radial direction
at a predetermined magnitude. The rear cover part 28 is a portion that covers the
flange part 12 of the reinforcing ring 10 from the outer side. The lining part 29
is a portion that covers the reinforcing ring 10 from the inner side and the inner
periphery side.
[0027] Note that the elastic body part 20 is integrally formed of the elastic material,
and the seal lip 21, the dust lip 22, the side lip 23, the lip waist portion 24, the
gasket part 27, the rear cover part 28, and the lining part 29 are respective portions
of the elastic body part 20 that is integrally formed of the elastic material.
[0028] As illustrated in Figs. 1, 2, the side lip 23 includes a distal end portion 31, a
middle portion 32, and a root portion 33. The root portion 33 is an annular portion
extending in the direction of the axis x. The middle portion 32 is a portion that
is connected to the root portion 33 and is on the outer side of the root portion 33,
and is an annular portion that increases in diameter toward the outer side in the
direction of the axis x. The distal end portion 31 is a portion that is connected
to the middle portion 32 and is on the outer side of the middle portion 32, and is
an annular portion that increases in diameter toward the outer side in the direction
of the axis x. In the side lip 23, the distal end portion 31 is bent to the inner
periphery side from the middle portion 32. More particularly, in the elastic body
part 20, the side lip 23 extends outwardly from an outer side portion of the lip waist
portion 24, and the root portion 33 extends outwardly from the lip waist portion 24.
The middle portion 32 extends outwardly from the outer end portion of the root portion
33, and the distal end portion 31 extends outwardly from the outer end portion of
the middle portion 32. Note that the side lip 23 may include no root portion 33, and
the middle portion 32 may extend from the lip waist portion 24.
[0029] An inner peripheral surface 31a that is a surface on the inner periphery side of
the distal end portion 31 and an inner peripheral surface 32a that is a surface on
the inner periphery side of the middle portion 32 are connected at an inner peripheral
connection portion c1 that forms an annular line. An outer peripheral surface 31b
that is a surface on the outer periphery side of the distal end portion 31 and an
outer peripheral surface 32b that is a surface on the outer periphery side of the
middle portion 32 are connected in an outer peripheral connection portion c2 that
forms an annular line.
[0030] More particularly, the distal end portion 31 has a conical cylindrical shape centered
about the axis x, the middle portion 32 has a conical cylindrical shape centered about
the axis x, and the root portion 33 has a cylindrical shape centered about the axis
x. As described above, the distal end portion 31 is bent to the inner periphery side
from the middle portion 32 such that an angle (angle α) between a generating line
of the inner peripheral surface 31a or the outer peripheral surface 31b of the distal
end portion 31 and the axis x is smaller than an angle (angle β) between a generating
line of the inner peripheral surface 32a or the outer peripheral surface 32b of the
middle portion 32 and the axis x (see Fig. 1).
[0031] As illustrated in Fig. 2, a thickness of the distal end portion 31, i.e., a width
between the inner peripheral surface 31a and the outer peripheral surface 31b of the
distal end portion 31 is a fixed thickness or a substantially fixed thickness w1,
and an inclination angle that is an angle between the generating line of the distal
end portion 31 and a line that extends in the radial direction and is perpendicular
to the axis x is an inclination angle θ. A length in the direction of the axis x of
the inner peripheral surface 31a of the distal end portion 31 is a length 11. A diameter
of the distal end portion 31 at a distal end 34 that is an outer end portion (distal
end of the side lip 23) of the inner peripheral surface 31a of the distal end portion
31 is a diameter φ.
[0032] As illustrated in Fig. 2, a thickness of the middle portion 32, i.e., a width between
the inner peripheral surface 32a and the outer peripheral surface 32b of the middle
portion 32 is a fixed thickness or a substantially fixed thickness w2, and a length
in the direction of the axis x of the inner peripheral surface 32a of the middle portion
32 is a length 12. As illustrated in Fig. 2, a thickness of the root portion 33, i.e.,
a width between the inner peripheral surface 33a and the outer peripheral surface
33b of the root portion 33 is a fixed thickness or a substantially fixed thickness
w3, and a length in the direction of the axis x of the inner peripheral surface 33a
of the root portion 33 is a length 13.
[0033] As illustrated in Fig. 2, in a connection portion between the distal end portion
31 and the middle portion 32, the inner peripheral connection portion c1 of the inner
peripheral surfaces 31a, 32a is positioned on the inner side of the outer peripheral
connection portion c2 of the outer peripheral surfaces 31b, 32b in the direction of
the axis x. That is, in the distal end portion 31, the inner peripheral surface 31a
is longer than the outer peripheral surface 31b in the direction of the axis x.
[0034] In the sealing device 1 in the usage state as described later, the distal end portion
31 of a side lip 23 is bent from the middle portion 32, dimensions of the distal end
portion 31 and the middle portion 32 are set, and a physical property of the elastic
body forming the elastic body part 20 is set, to set a contact pressure to the deflector
at the distal end portion 31 with respect to a contact pressure to the deflector at
the middle portion 32 such that the contact between the distal end 34 of the side
lip 23 and the deflector is not released. That is, in the differential device, when
the axle is displaced due to being loose, and a contact width of the side lip 23 extends
to the middle portion 32 beyond the distal end portion 31, the distal end portion
31 is bent from the middle portion 32, and the dimensions of the distal end portion
31 and the middle portion 32 are set, and the physical property of the elastic body
of the elastic body part 20 is set such that the contact pressure of the distal end
34 of the side lip 23 with the deflector is larger than the contact pressure of the
middle portion 32 with the deflector in this contact width to prevent the distal end
34 of the side lip 23 from floating away from the deflector.
[0035] Specifically, the thickness w1 of the distal end portion 31 of the side lip 23 is
set based on a hardness of the elastic body forming the elastic body part 20, i.e.,
based on a hardness of the elastic body forming the side lip 23. More specifically,
the hardness of the elastic body forming the side lip 23 and the thickness w1 of the
distal end portion 31 are set so that the distal end portion 31 is flexible to prevent
the distal end 34 from floating away even when the contact width is increased as described
above. The greater the thickness w1 of the distal end portion 31, the more strongly
the side lip 23 is in contact with the deflector to enhance the performance of preventing
entry of foreign matter from the outside. However, when the deflector is slided, a
sliding resistance generated between the side lip 23 and the deflector is increased,
thereby easily generating heat. Due to this, the wear and the thermal deterioration
of the side lip 23 are accelerated, thereby reducing the durability of the side lip
23. Thus, it is preferable that the thickness w1 of the distal end portion 31 be set
in view of the durability of the side lip 23. The thickness w1 of the distal end portion
31 of the side lip 23 is w1 = 0.7 mm to 1.6 mm, for example.
[0036] The inclination angle θ of the distal end portion 31, the length 11 of the distal
end portion 31, and the length 12 of the middle portion 32 are set with respect to
each other. Specifically, the inclination angle θ of the distal end portion 31 is
θ = 60° to 85°, for example, the length 11 of the distal end portion 31 is 11 = 1.5
mm to 4.5 mm, for example, and the length 12 of the middle portion 32 is 12 ≥ 1.5
× 11, for example.
[0037] The length 11 of the distal end portion 31 is set to such a length that a contact
width δ in a range where the side lip 23 is in contact with an inner surface (sliding
surface) of the deflector does not reach a range of the inner peripheral surface 32a
of the middle portion 32 beyond a range of the inner peripheral surface 31a of the
distal end portion 31 in a state where the sealing device 1 is attached to a desired
position of the transaxle (see Fig. 2). The inclination angle θ of the distal end
portion 31 is set to such an angle that the distal end portion 31 that is in contact
with the deflector in the transaxle is prevented from being buckled or damaged.
[0038] Next, operation of the sealing device 1 having the above-described configuration
will be described. Fig. 3 is a diagram for illustrating the sealing device 1 in a
state of being attached to a transaxle 50, and a partial enlarged cross-sectional
view along the axis x enlargedly illustrating the vicinity of the sealing device 1
in the transaxle 50. Note that Fig. 3 illustrates a state where the sealing device
1 is attached to a desired position of the transaxle 50 (hereinafter referred to as
an "initial state"). That is, the sealing device 1 is attached to the transaxle 50
in a manner such that the distal end portion 31 of the side lip 23 is in contact with
a sliding surface 53 of an annular deflector 52 by a desired contact width δ, the
deflector 52 being fixed to an axle 51 as an output shaft of the differential mechanism
(not illustrated) of the transaxle 50. The transaxle 50 is a well-known transaxle
(see Fig. 11), and a detailed description of the configuration is omitted herein.
Note that the deflector 52 may be formed of a member separate from the axle 51, or
the deflector 52 may be formed by forming a part of the axle 51 to be annularly projected
toward the outer periphery side.
[0039] As illustrated in Fig. 3, the sealing device 1 is fitted to a through-hole 55 formed
in a housing 54 of the transaxle 50. The axle 51 is rotatably inserted through the
through-hole 55. Note that the transaxle 50 is provided with two through-holes and
two axles for right and left wheels, but the through-holes and the axles corresponding
to respective wheels have similar configurations, respectively, and the through-hole
55 and the axle 51 correspond to each of the right and left wheels, respectively.
[0040] In the through-hole 55 in the housing 54, a space between an outer peripheral surface
51a of the axle 51 and an inner peripheral surface 55a of the through-hole 55 is sealed
by the sealing device 1. Specifically, the cylindrical part 11 of the reinforcing
ring 10 is fitted to the through-hole 55, the gasket part 27 of the elastic body part
20 is compressed between the cylindrical part 11 and the inner peripheral surface
55a of the through-hole 55 so that the gasket part 27 is in close contact with the
inner peripheral surface 55a of the through-hole 55, thereby sealing between the sealing
device 1 and the through-hole 55 on the outer periphery side. The lip distal end portion
25 of the seal lip 21 of the elastic body part 20 is in contact with the outer peripheral
surface 51a of the axle 51 so that the axle 51 is slidable, thereby sealing between
the sealing device 1 and the axle 51 on the inner periphery side. Thus, the lubricant
stored in the housing 54 is prevented from leaking out to the outside.
[0041] The distal end edge of the dust lip 22 is in contact with the outer peripheral surface
51a of the axle 51 so that the axle 51 is slidable, thereby preventing foreign matter
from entering into the housing 54 from the outside. In the side lip 23, the distal
end edge in the inner peripheral surface 31a in a range of the contact width δ of
the distal end portion 31 is in contact with the sliding surface 53 of the deflector
52, thereby preventing the foreign matter from entering into the housing 54 from the
outside.
[0042] Fig. 4 is an enlarged cross-sectional view of the side lip 23 for illustrating a
state of the side lip 23 in the initial state. As illustrated in Fig. 4, in the initial
state, the distal end portion 31 of the side lip 23 is partially curved or is elastically
deformed, and the inner peripheral surface 31a of the distal end portion 31 is in
contact with the sliding surface 53 of the deflector 52 in a range of a contact width
δ0 from the distal end 34.
[0043] In the transaxle 50, the axle 51 may be displaced inwardly in the direction of the
axis x so that the sliding surface 53 of the deflector 52 is displaced in the direction
of the axis x, or the axle 51 may be inclined with respect to the axis x so that the
sliding surface 53 of the deflector 52 may be inclined, due to dimensional tolerance
and assembly errors of each configuration. When the transaxle 50 is operated, the
axle 51 may be displaced in the direction of the axis x or displaced diagonally with
respect to the axis x based on the gap between respective configurations. If such
a displacement (looseness) occurs, the contact width δ of the side lip 23 with respect
to the deflector 52 is increased as illustrated in Fig. 5. In the side lip 23 in the
sealing device 1, the distal end portion 31 is bent from the middle portion 32 on
the root side toward the inner periphery side as described above. Thus, even when
the contact width δ is increased, the contact pressure of the distal end 34 with respect
to the deflector 52 is not largely reduced, and a difference between the contact pressure
of the distal end 34 with respect to the deflector 52 and the contact pressure of
the portion on the root side does not become so small that the distal end 34 of the
side lip 23 floats away from the sliding surface 53 of the deflector 52.
[0044] Specifically, as illustrated in Fig. 5, even when a considerable looseness occurs
in the axle 51, and the contact width δ is increased and becomes a contact width δ1
in which the side lip 23 contacts the sliding surface 53 of the deflector 52 at also
the inner peripheral surface 32a of the middle portion 32 beyond the inner peripheral
surface 31a of the distal end portion 31 toward the root side, the distal end 34 can
be prevented from floating away from the sliding surface 53 of the deflector 52. In
the state of the larger contact width δ1 as illustrated in Fig. 5, in the side lip
23, a contact pressure p1 of the distal end 34 with respect to the deflector 52 is
not largely reduced, and a difference Δp between the contact pressure p1 and a contact
pressure p2 at a portion of the middle portion 32 on the root side can be prevented
from becoming so small that the distal end 34 floats away from the sliding surface
53 of the deflector 52, as illustrated in Fig. 6.
[0045] Next, the sealing performance of the sealing device 1 having the above-described
configuration will be described. Specifically, the sealing device 1 according to the
embodiment of the present invention and the conventional sealing device 100 illustrated
in Figs. 10 and 11 were subjected to the evaluation test of the sealing performance,
to evaluate the presence of floating of the side lip 23, 105 away from the deflector
52, 113, and a relationship between the contact pressure and the contact position
of the side lip 23, 105 with respect to the deflector 52, 113.
[0046] In the evaluation test of the sealing performance, each of the sealing device 1 and
the conventional sealing device 100 was attached to a sealing performance tester 200
illustrated in Fig. 7, and the presence of the floating of the distal end portion
of the side lip 23, 105 and the relationship between the contact pressure and the
contact position were evaluated. The evaluation test and the evaluation results will
be described with reference to Figs. 7 to 9. Fig. 7 is a diagram for illustrating
a schematic configuration of the sealing performance tester 200 used for the above-described
evaluation test of the sealing performance. Fig. 8 is a diagram for showing results
of the evaluation test of the sealing performance of the conventional sealing device
100 illustrated in Fig. 10, Fig. 8(a) is a diagram illustrating a projection image
of the side lip 105 in the evaluation test of the sealing performance, and Fig. 8(b)
is a diagram showing the relationship between the contact position and the contact
pressure of the side lip 105. Fig. 9 is a diagram for showing results of the evaluation
test of the sealing performance of the sealing device 1 according to the embodiment
of the present invention, Fig. 9(a) is a diagram illustrating a projection image of
the side lip 23 in the evaluation test of the sealing performance, and Fig. 9(b) is
a diagram showing the relationship between the contact position and the contact pressure
of the side lip 23.
[0047] As illustrated in Fig. 7, the sealing performance tester 200 used for the above-described
evaluation test of the sealing performance includes an axle corresponding part 201
corresponding to the axle 51 with which the lip distal end portion 25 of the seal
lip 21 and the dust lip 22 can be in contact, a deflector corresponding part 202 corresponding
to the deflector 52 with which the distal end 34 of the side lip 23 can be in contact,
and a housing corresponding part 203 corresponding to the housing 54 to which the
gasket part 27 is fitted. That is, the sealing performance tester 200 is configured
to be able to reproduce the state where the sealing device 1 is attached to the transaxle
50 (see Fig. 3) using the axle corresponding part 201 corresponding to the axle 51,
the deflector corresponding part 202 corresponding to the deflector 52, and the housing
corresponding part 203 corresponding to the housing 54.
[0048] The sealing performance tester 200 includes a light source 204 that emits light to
the side lip 23, and an imaging part 205 that emits a projection image of the side
lip 23 irradiated with light at a position facing the light source 204. Note that
Fig. 7 illustrates a case where the sealing device 1 is attached to the sealing performance
tester 200, but, to perform the evaluation test of the sealing performance of the
conventional sealing device 100 illustrated in Fig. 10 and Fig. 11, the conventional
sealing device 100 can be also attached to the sealing performance tester 200. That
is, the sealing performance tester 200 is configured to be able to reproduce the state
where the conventional sealing device 100 is attached to the transaxle (see Fig. 11)
using the axle corresponding part 201, the deflector corresponding part 202, and the
housing corresponding part 203.
[0049] The axle corresponding part 201 of the above-described sealing performance tester
200 can reciprocate at a predetermined speed and a predetermined amplitude in the
direction of the axis x by a motor (not illustrated) and, by this reciprocation, the
displacement of the axle 51 can be reproduced. In the evaluation test of the sealing
performance, the axle corresponding part 201 was made to reciprocate in the direction
of the axis x to thereby make the deflector corresponding part 202 reciprocate in
the direction of the axis x, and then the projection image of the side lip 23, 105
was imaged by the imaging part 205 when a sliding surface corresponding part 210 reciprocated
in the direction of the axis x, then the contact state of the side lip 23, 105 was
observed. In the evaluation test, the axle corresponding part 201 was moved by a moving
width of 2.81 mm and at a moving speed of 4 Hz in the direction of the axis x. In
the evaluation test, the axle corresponding part 201 was made reciprocate at a width
of 2.81 mm as a whole inwardly and outwardly in the direction of the axis x making
as a reference position the state where the side lip 23, 105 is in contact with the
sliding surface corresponding part 210 at a maximum interference of the predetermined
interference width.
[0050] Fig. 8 and Fig. 9 show the results of the evaluation tests of the conventional sealing
device 100 and the sealing device 1 according the embodiment of the present invention,
respectively. Fig. 8 and Fig. 9 show the states of side lip 105, 23 in a state where
the axle corresponding part 201 is moved by the maximum width inwardly from the reference
position, that is, a state where the side lip 23, 105 is maximally pressed against
the sliding surface corresponding part 210.
[0051] As illustrated in Fig. 8(a), in the conventional sealing device 100, a gap s was
found between the distal end 121 of the side lip 105 and the sliding surface corresponding
part 210 of the deflector corresponding part 202. As shown in Fig. 8(b), in the conventional
sealing device 100, it was found that when the contact width of the side lip 105 reaches
the middle portion 122 beyond the distal end portion 120, the contact pressure of
the side lip 105 with the sliding surface corresponding part 210 becomes the maximum
at the middle portion 122, and the contact pressure at the distal end 121 is greatly
lower than the contact pressure at the middle portion 122.
[0052] On the other hand, as illustrated in Fig. 9(a), in the sealing device 1 according
to the embodiment of the present invention, it was found that the distal end 34 of
the side lip 23 does not float away from the sliding surface corresponding part 210
of the deflector corresponding part 202. As shown in Fig. 9(b), in the sealing device
1, it was found that when the contact width of the side lip 23 reaches the middle
portion 32 beyond the distal end portion 31, the contact pressure of the side lip
23 with the sliding surface corresponding part 210 becomes the maximum at the distal
end 34, and the contact pressure at the distal end 34 is larger than the contact pressure
at the middle portion 32, resulting that the distal end 34 does not float away from
the sliding surface corresponding part 210.
[0053] Thus, in the sealing device 1, the distal end portion 31 that is a portion on the
distal end side of the side lip 23 is bent toward the inner side with respect to the
middle portion 32, and therefore the contact pressure of the distal end 34 of the
side lip 23 with respect to the deflector 52 can be prevented from being reduced even
when the contact width δ of the side lip 23 with respect to the sliding surface 53
of the deflector 52 is increased because of a large looseness of the axle 51. Thus,
the contact pressure of the distal end 34 of the side lip 23 with respect to the deflector
52 can be maintained at a magnitude larger than the contact pressure of a portion
on the root side in the contact width range of the side lip 23 so that the distal
end 34 does not float away from the sliding surface 53 of the deflector 52. Accordingly,
the distal end 34 of the side lip 23 can be prevented from floating away from the
sliding surface 53 of the deflector 52 even when the contact width δ is increased,
and further the foreign matter can be prevented from entering the inside over the
side lip 23.
[0054] Thus, according to the sealing device 1 for a differential mechanism according to
the embodiment of the present invention, the distal end 34 of the side lip 23 can
be prevented from floating away from the deflector 52 even when the contact width
δ of the side lip 23 is increased.
[0055] Although the embodiment of the present invention has been described above, the present
invention is not limited to the sealing device 1 for a differential mechanism according
to the embodiment of the present invention, and includes any modes falling within
the scope of the concept and claims of the present invention. Respective configurations
may be appropriately selectively combined to solve at least part of the above-described
problems and achieve at least part of the above-described effects. For example, in
the above-described embodiment, the shape, material, arrangement, size and the like
of each component can be appropriately changed according to a specific use mode of
the present invention.
List of Reference Signs
[0056]
1, 100 sealing device
10, 101 reinforcing ring
11 cylindrical part
12 flange part
20, 102 elastic body part
21, 103 seal lip
22, 104 dust lip
22a projection
23,105 side lip
24 lip waist portion
25 lip distal end portion
25a taper surface
25b screw projection
26 garter spring
27 gasket part
28 rear cover part
29 lining part
31, 120 distal end portion
31a, 32a, 33a inner peripheral surface
31b, 32b, 33b outer peripheral surface
32,122 middle portion
33 root portion
34, 121 distal end
50 transaxle
51, 111 axle
51a outer peripheral surface
52, 113 deflector
53, 113a sliding surface
54, 112 housing
55,114 through-hole
55a inner peripheral surface
200 sealing performance tester
201 axle corresponding part
202 deflector corresponding part
203 housing corresponding part
204 light source
205 imaging part
210 sliding surface corresponding part
c1 inner peripheral connection portion
c2 outer peripheral connection portion
l1, l2, l3 length
p, p1, p2 contact pressure
s gap
Δp, Δpc pressure difference
x axis
w1, w2, w3 thickness
δ, δ1, δ2 contact width
θ inclination angle
φ diameter